Alternative Fuels

Methanol Vs. Anhydrous Ammonia … or maybe a Hybrid?

Methanol Economy

The methanol economy is a suggested future economy in which methanol replaces fossil fuels as a mean of energy storage, fuel and raw material for synthetic hydrocarbons and their products. It offers an alternative to the proposed hydrogen economy or ethanol economy.

Methanol is a fuel for heat engines and fuel cells.Due to its high octane rating it can be used directly as a fuel in cars (including hybrid and plug-in vehicles) using existing internal combustion engines (ICE). Methanol can also be used as a fuel in fuel cells, either directly in Direct Methanol Fuel Cells (DMFC) or indirectly after conversion into hydrogen by reforming.

Methanol is a liquid under normal conditions, allowing it to be stored, transported and dispensed easily, much like gasoline and diesel fuel nowadays. It can also be readily transformed by dehydration into dimethyl ether, a diesel fuel substitute with a cetane number of 55.

Methanol is already used today on a large scale (about 37 million tonnes per year)[3] as a raw material to produce numerous chemical products and materials. In addition, it can be readily converted in the methanol to olefin (MTO) process into ethylene and propylene, which can be used to produce synthetic hydrocarbons and their products, currently obtained from oil and natural gas.

Methanol can be efficiently produced from a wide variety of sources including still abundant fossil fuels (natural gas, coal, oil shale, tar sands, etc.), but also agricultural products and municipal waste, wood and varied biomass. More importantly, it can also be made from chemical recycling of carbon dioxide. Initially the major source will be the CO2 rich flue gases of fossil fuel burning power plants or exhaust of cement and other factories.In the longer range however, considering diminishing fossil fuel resources and the effect of their utilization on earth’s atmosphere, even the low concentration of atmospheric CO2 itself could be captured and recycled via methanol, thus supplementing nature’s own photosynthetic cycle. Efficient new absorbents to capture atmospheric CO2 are being developed, mimicking plant life’s ability. Chemical recycling of CO2 to new fuels and materials could thus become feasible, making them renewable on the human timescale.

Today methanol is produced exclusively from syngas, a mixture of H2, CO and CO2 obtained by partial oxidation of fossil fuels, mainly natural gas and coal. This technology is well developed and operated on a large scale.

In 2005 Nobel prize winner George A. Olah advocated the methanol economy in an essay [1] and in 2006 he and two co-authors published a book around this theme.

Today methanol is produced exclusively

from syngas, a mixture of:

Hydrogen Gas (H2 )

Carbon Dioxide (CO2)

Cobalt (CO)

Carbon Capture and Storage (CCS)

Carbon capture and storage (CCS) is an approach to mitigateglobal warming by capturing carbon dioxide (CO2) from large point sources such as fossil fuel power plants and storing it instead of releasing it into the atmosphere. Technology for large scale capture of CO2 is already commercially available and fairly well developed. Although CO2 has been injected into geological formations for various purposes, the long term storage of CO2 is a relatively untried concept and as yet (2007) no large scale power plant operates with a full carbon capture and storage system.

CCS applied to a modern conventional power plant could reduce CO2 emissions to the atmosphere by approximately 80-90% compared to a plant without CCS[1]. Capturing and compressing CO2 requires much energy and would increase the fuel needs of a coal-fired plant with CCS by about 25%[1]. These and other system costs are estimated to increase the cost of energy from a new power plant with CCS by 21-91%[1]. These estimates apply to purpose-built plants near a storage location: applying the technology to preexisting plants or plants far from a storage location will be more expensive.

Storage of the CO2 is envisaged either in deep geological formations, in deep ocean masses, or in the form of mineral carbonates. In the case of deep ocean storage, there is a risk of greatly increasing the problem of ocean acidification, a problem that also stems from the excess of carbon dioxide already in the atmosphere and oceans. Geological formations are currently considered the most promising sequestration sites, and these are estimated to have a storage capacity of at least 2000 Gt CO2 (currently, 30 Gt per year of CO2 is emitted due to human activities[2]). IPCC estimates that the economic potential of CCS could be between 10% and 55% of the total carbon mitigation effort until year 2100 (Section 8.3.3 of IPCC report[1]).

Cobalt

Used in superalloys for jet engines, chemicals (paint driers, catalysts, magnetic coatings, pigments, rechargeable batteries), magnets, and cemented carbides for cutting tools. Principal cobalt producing countries include Democratic Republic of the Congo, Zambia, Canada, Cuba, Australia, and Russia. The United States uses about one-third of total world consumption. Cobalt resources in the United States are low grade and production from these deposits is usually not economically feasible.

The ocean floor has nodules of metals that form when hot water from deep in the Earth comes into contact with the cold ocean water. These nodules are mostly manganese and so are called manganese nodules. It is estimated that there are millions of tons of cobalt in these nodules. Presently, we do not have the technology to retrieve these nodules at a reasonable cost.

Cobalt is not a particularly rare metal and it ranks 33 in abundance. It is however widely scattered in the Earth’s crust but is found in potentially exploitable quantities in several countries, 17 of which currently produce.

Cobalt is only extracted alone from the Moroccan and Canadian Arsenide ores. It is normally associated with copper or nickel. 39% of World production is from Africa – D.R.C. (21%) and Zambia (15%) – where cobalt is a copper by-product.

Where Cobalt is Mined: Significant resources of cobalt are also present in the deep sea nodules and crusts which occur in the Mid-Pacific and are estimated to contain anywhere from 2.5-10 million tonnes (metric tons) of cobalt. At a world production level of 27,000 tonnes, this is 90 to 400 years of usage. Current land sources are estimated at over 100 years, so no long term shortage is in sight.

Anhydrous Ammonia

Anhydrous ammonia (ammonia without water) can be a substitute for petroleum as a transportation fuel. It has the potential to make the hydrogen economy a reality in the near-term, at an affordable cost. It is an energy form that is manufactured. It can be made from all primary energy sources so production sources can be diversified or production can focus on the cheapest, cleanest and greenest source. Ammonia can be used in internal combustion engines with minor modifications. It can be used in gas turbines and ammonia fuel cells are being developed. Substantial ammonia distribution infrastructure already exists in the Midwest. Other existing infrastructure can be converted. The existing retail fuel dispensing infrastructure can be converted to ammonia. Although there are safety issues with ammonia, the issues are no more severe than those with gasoline and diesel fuel.

An ammonia molecule is composed of one atom of nitrogen and three atoms of hydrogen (NH3) and is commonly found in nature. The great majority of ammonia in the environment comes from the natural breakdown of manure and dead plants and animals. When ammonia combusts it produces nitrogen and water vapor (4NH3 + 3O2 yields 2N2 + 6H2O)

Ammonia Powered Internal Combustion Engines

Gasoline and diesel fuel internal combustion engines can be converted to run on ammonia. The first utilization of liquid anhydrous ammonia as a fuel for motor-buses took place in Belgium during the year 1943. The motor-bus fleet logged thousands of miles during WWII with no difficulties.

Ammonia has a high octane rating (about 120 versus gasoline at 86-93). So it does not need an octane enhancer and can be used in high compression engines. However, it has a relatively low energy density per gallon – about half of gasoline. The fuel mileage of ammonia is about half of gasoline’s mileage.

Along with hydrogen, ammonia is the only fuel that has no carbon emission when combusted because it doesn’t contain carbon. It may contribute a small amount of nitrous oxide emission, which can be controlled.

Ammonia can also be used in diesel engines. However, ammonia will not compression ignite except at very high pressures. So a small amount of high-cetane (the combustion quality during compression ignition) fuel is added. Research is showing that a 5 percent biodiesel and 95 percent ammonia blend works well in farm machinery.

Ammonia Production

Ammonia can be produced from a variety of renewable energy sources. For example, wind energy (February 2009 article) can be used to create hydrogen through the electrolysis cracking of water into hydrogen and oxygen. Ammonia can also be produced from solar energy, municipal sewage systems, nuclear power, geothermal energy, ocean and tidal energy and others.

Currently ammonia is produced primarily from natural gas and coal. China is the number one producer. Currently U.S. ammonia is made primarily from natural gas. Hydrogen is taken from the natural gas and nitrogen comes from the atmosphere. Although U.S. ammonia has traditionally been produced domestically, imports of ammonia have increased substantially in recent years due to the high price of U.S. natural gas versus foreign natural gas.

Natural gas produces greenhouse gases. So, although ammonia does not produce greenhouse gases during combustion, the production of ammonia from natural gas does emit greenhouse gases. Carbon sequestration at the point of production could greatly reduce these emissions. However, carbon capture and sequestration technology is still in the developmental stage and would add additional cost to the fuel. If this technology is developed, it will provide a carbon free transportation fuel from the use of natural gas and coal.

Ammonia Safety

Although ammonia has a good safety track record, it has safety concerns if used as a transportation fuel for motor vehicles. Ammonia is safer than propane and comparable to the safety of gasoline when used as a transportation fuel. Ammonia vapors cause irritation to humans at low concentrations and is life threatening at high concentrations. This is because ammonia can pull the water out of human tissue. However, ammonia can easily be detected by its strong odor. It is lighter than air and rapidly dissipates in the atmosphere. Regardless, safety precautions need to be implemented for fueling stations where the ammonia is transferred from trucks to storage tanks and from pumps to motor vehicles. In addition, there are also safety issues for the storage of ammonia onboard motor vehicles. Research is underway to develop new and improved ammonia tanks, fittings and tubing to ensure safe operation.

There are also positive safety aspects to ammonia when compared to gasoline. Gasoline may produce carcinogenic vapors but ammonia is not carcinogenic. Ammonia does not burn readily or sustain combustion except under narrow fuel-to-air mixtures of 15-25% air. Explosions and fire are less likely with a ruptured ammonia tank than with gasoline. Also, gasoline can produce carbon soot particles that are hazardous when breathing. Because ammonia contains no carbon, it cannot produce soot.

Ammonia and Fuel Cells

We often hear that hydrogen is our ultimate renewable and green fuel source. Hydrogen fuel cells take in hydrogen (H2) and oxygen (O2), produce electricity to power the motor vehicle and emit water (H2O). Hydrogen is the most abundant element in the universe but it is relatively rare in its elemental (H2) form on earth. Although hydrogen has high energy density by weight, it is the lightest of all elements and requires large volumes to power a motor vehicle. So, elemental hydrogen is difficult to store and transport. Hydrogen volumes can be reduced by compressing it as either compressed hydrogen or liquid hydrogen. However, the pressures required to do either of these are substantial and create a potential safety hazard.

Ammonia is sometimes called the “other hydrogen” due to its structure of three hydrogen molecules and one nitrogen molecule. The ability of ammonia gas to become a liquid at low pressures means that it is a good “carrier” of hydrogen. Liquid ammonia contains more hydrogen by volume than compressed hydrogen or liquid hydrogen. For example, ammonia is over 50% more energy dense per gallon than liquid hydrogen. So ammonia can be stored and distributed easier than elemental hydrogen. Fueling stations are much easier to convert to dispensing ammonia than elemental hydrogen. Ammonia could be stored onboard a motor vehicle where the elemental hydrogen and nitrogen are separated just before the hydrogen is fed into the fuel cell.

In addition to hydrogen fuel cells there are several fuel cells designed to use ammonia directly. This would eliminate the need to separate the ammonia into its hydrogen and nitrogen elements before it is used in the fuel cell. These cells enable high efficiency conversion of ammonia to electric power.

Industry Considerations

Moving to an ammonia/hydrogen economy has policy implications. Although the ultimate vision is to make large amounts of ammonia from a variety of renewable energy sources, ammonia in the interim will need to be made from natural gas. Care must be used to not adversely impact the use of ammonia as a nitrogen fertilizer. Increasing the demand for ammonia could adversely impact the price and availability of nitrogen fertilizer for farmers unless supplies are expanded along with demand. This could potentially impact cropping patterns in the U.S. and elsewhere. The impact on electric power generation which is also a larger user of natural gas must be taking into account.